A vehicle driveline may include a universal joint (U-joint) between an output of a transmission and input to a differential to allow vertical motion between the transmission and the differential. The U-joint may be located between two driveshaft halves, one driveshaft half coupled to the transmission and the other driveshaft coupled to the differential. The U-joint and driveshaft halves may have a natural resonance frequency that is within the expected driveline rotational frequency range. If the driveline is rotated at its resonance frequency, the driveline may begin to oscillate and transfer motion to the vehicle chassis. Therefore, it would be desirable to avoid the driveline's resonance frequency, but avoiding the drivelines natural frequency may not be possible at all times. One way to reduce vehicle driveline oscillations may be to slip a torque converter lockup clutch when vehicle speed is within a specified vehicle speed range. However, slipping the torque converter lockup clutch may consume fuel and degrade clutch performance.
The inventors herein have recognized the above-mentioned issues and have developed a driveline operating method, comprising: adjusting torque of a generator in a driveline in response to a band pass filtered driveline speed in a first mode; and adjusting slip of a clutch in the driveline in response to the band pass filtered driveline speed in a second mode in response to a generator condition.
By adjusting torque output of a driveline motor/generator in response to a band pass filtered driveline speed, it may be possible to provide the technical result of limit vehicle NVH while improving vehicle fuel economy. In particular, it may be more efficient to cancel driveline speed oscillations when a driveline motor/generator has sufficient torque capacity to reduce the driveline speed oscillations. Further, when the driveline motor/generator is at a condition where it does not have capacity to reduce the driveline speed oscillation to less than a threshold speed oscillation, a driveline clutch may be commanded to slip to allow the vehicle to continue to operate at its present speed.
The present description may provide several advantages. In particular, the approach may reduce driveline speed oscillations during different driveline operating conditions. Further, the approach provides for selecting a driveline speed sensor that provides a higher resolution driveline speed so that compensation may be provided during varying driveline conditions. Additionally, by band pass filtering the driveline speed signal, it may be possible to provide compensation that cancels only driveline resonance frequencies.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.